


For darkness I became

by chiapslock



Series: Shiro Birthday Month [10]
Category: Voltron: Legendary Defender
Genre: Angst with a Happy Ending, Demon!Keith, M/M, Paranormal Investigators, Shiro and Matt as paranormal investigators, alternative universe
Language: English
Status: Completed
Published: 2018-02-13
Updated: 2018-02-13
Packaged: 2019-03-17 13:25:17
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,080
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13659903
Author URL: https://archiveofourown.org/users/chiapslock/pseuds/chiapslock
Summary: Shiro knows the consequences of forming a pact with a demon, but to save his business parter and best friend he throws caution to the wind: the loss of his soul is worth having Matt back.However Keith, the demon he has formed a pact with, seems different from what he expected.





	For darkness I became

**Author's Note:**

>   
>  I didn't have time to re-read this. So I'm hoping I will tomorrow... I'm really sorry! D: I hope you can forgive me! I hope it isn't too terrible!  
> But for now Demon!Keith is my jam. 

"You do know that's a demon, right?" Pidge asks him from where she's perched on top of the ladder and he looks behind him at the being following him and then stares at his ears, who sprout from his head and looks exactly like cat ears.

"Yes," he answers, as deadpan as he can, "I did suspect it."

Keith's tail, who is more fluffy than anything Shiro has ever seen, twitches behind him—if out of amusement or annoyance, Shiro doesn't know.

"You didn't sign a contract with him, right?" Pidge continues, staring at the two of them almost as if she could see the ties keeping them together.

Shiro huffs and shakes his head. "I'm not a novice, I don't run along forming contracts with every demon I see," he tells her, walking towards his study. WIth his head he motions for Keith to follow him, and the other does without saying anything.

After he closes the door, which it's spelled with a silencing charm, he looks back at the demon currently inspecting his office. This might be awkward.

"I'm sorry about Pidge," he tries, with a smile, "she's a little paranoid."

"You did go and form a contract with me in her defence," Keith replies immediately with a little smile. He looks amused at the situation, like these human squabbles are just so beneath him.

"Yeah, but you're not the first demon I've seen in my life, just the first one I made a contract with. So, I think I'm still ahead," he says, and the other looks at him a little concerned.

"You've tried this before?" Keith asks, and there is something under his voice—some kind of possessiveness and worry—that makes Shiro's skin prickle.

"No," he replies immediately, "but in my line of work, your kind does come up."

He's not even lying.

Shiro hasn't been a paranormal investigator for a long time, but he has had his fair share of experiences with Keith's kind. Well, maybe not exactly like Keith.

It had been a stupid game, that started when he and Matt had decided they wanted proof that ghosts existed. They had been stupid kids then, with cameras that didn't even work properly.

He looks at Keith and his fangs and wonders how stupid is he really to be doing this.

"So you will help me right?" Shiro asks, in the end, walking towards his own desk.

Keith studies his movements, just like a cat, and Shiro wonders what's in his mind. How does Keith see him, a human so powerless that he had to ask the help of a demon to save his own best friend.

"That is the deal we have made," Keith answers, shrugging.

Indeed, it is.

  
  


Shiro still doesn’t know if what he’s doing it’s even going to make a difference. He had been desperate, after he had tried once again to save Matt from the demon who had taken him, with no result.

Their whole business had been born when Shiro and Matt had been fresh out of high school, two stupid college kids who were too stupid to know better. They had hunted their fist ghost with barely working equipment and no real knowledge of how Spirits worked.

They are alive out of sheer luck more than anything else.

Years later, they still think they are alive because of luck and nothing more, but at least they now have functioning equipments. He guesses it can be called progress.

Still, as it turns out, luck can’t keep them going forever. 

Matt had been taken, stolen under Shiro’s eyes. A demon had attacked, vicious in his fury, and while he had hurt Shiro badly enough to leave him whimpering on the ground, he had taken Matt and disappeared with him.

Honestly, usually they don’t deal with demons. Unlike what modern media will have you believe, demons don’t really deal with humans if the humans don’t go and poke them. So Shiro and Matt usually leave them be.

This time, it had been the demons going for them, even if Matt and Shiro had only been there to investigate an old manor, called Manor Altea.

Shiro had looked over the history of the place for days, after, with Pidge’s help. He had found nothing more than the original report and he still doesn’t understand why a demon as powerful as Zarkon would be interested.

Manor Altea’s history isn’t as violent as other houses they have been into. The family that lived vanished mysteriously out of the blue, leaving their daughter to inherit the whole fortune. She had become obsessed with finding her family and, later had died alone searching for them.

Now, years later, one of the family’s ancestors had asked Shiro and Matt to look into the apparition that have plagued the house for years. It had seemed like one of their usual jobs, really, but apparently they had been wrong.

When Shiro had returned back home, after having fought the demon, alone and bleeding, he had wondered what he was supposed to do now.

Everyone knew the dangers in his line of job, and they had met a lot of people who had told them to stop before something that couldn’t been undone happened.

Shiro guesses that is what they were referring to. 

He had tried to keep investigating on his own, but soon Pidge — Matt’s little sister — had come to him, demanding an explanation he hadn’t been able to give her. She had been relentless in her questions and now she serves as Shiro’s partner in their quest to bring Matt back.

But all their searches have never been particularly successful.

It’s what has brought Shiro to this, to contacting a demon and forming a pact with him. He had researched what kind of demon to call to his side for a long time, trying to see who could have been useful to him and crazy enough to help him fight a demon as strong as Zarkon.

Keith, all things considered, for what Shiro had gathered, isn’t a very old demon, but he’s renowned for his talent in battle and for his impetus nature.

Shiro had summoned him with burnt coal, a ritual knife to bind the other to the corporeal word and an evocation circle to made sure the demon couldn’t get out before they had made the contract.

Keith had responded to his call with an annoyed look and a slight aggressive snarl, but they had reached a compromise soon. Keith would have Shiro’s soul at the end of the mission, and Keith would help him to save Matt.

Pretty straightforward, if you ask Shiro. 

During the duration of the pact, before they save Matt, Shiro’s soul will stay in his body, pending the success of their mission.

But if it’s to save Matt, Shiro doesn’t really mind giving up his soul.

  
  


A week later Shiro has fallen asleep at his desk, like it’s usual these days, and he’s woken up by a scream and the sound of an explosion.

Shiro opens his eyes quickly and jumps, reaching for his gun. He feels twitchy and raw, but he doesn’t remember if he was dreaming about something.

He runs out of the room immediately, weapon drawn, and he sees Keith snarling at someone.

Lance is looking angrily at the demon, a talisman raised in his hand. Hunk, beside him, looks spooked. When everyone notices him entering the room, they all turn towards him, surprised.

“Shiro, what is going on?” Lance ask, pointing at Keith. Shiro hasn’t seen Lance in a while, he realizes.

They had told Pidge about the contract a couple of days before, in the end, after Shiro had adjusted to the idea. Pidge had looked sad, but understanding.

Lance won’t be happy, however, and Shiro  _ needs _ Lance. He doesn’t have a lot of magic powers, but he comes from a long line of witches and he helps as much as he can. 

For years he and Matt had gone to him and his family for help in research and protective spells. Now, Shiro can’t afford to lose any of his allies in this fight. Still, he can’t lie to them.

“Don’t worry, this is Keith. He’s not going to hurt you,” he says, stepping in front of the demon. Keith can probably protect himself, but if he defuses the situation as fast as he can, then maybe there is a possibility of actually containing the disaster.

Lance looks at Keith again, and he obviously stops to look at his ears and tails. The demon doesn’t really do anything, stays serious behind Shiro. It’s not unexpected, as much as the books had talked about Keith as a demon of violent urges and impetus, Keith rarely shows any emotion.

In the week they have been together, Keith had mostly been a silent companion in Shiro’s long nights spent in research.

“He’s a demon,” Lance states, unnecessary, and Shiro nods. There is no real need to confirm it, Lance says it without question in his voice. They have all been around enough to recognize the tell-tale sign of a demon.

Keith’s nature is obvious in his less than human form, and even if Lance’s magic powers aren’t up to standard, he has always been sensitive to evil forces. 

“Demons are never good news,” Hunk says, beside Lance, looking worriedly at Keith, “I thought you knew that.”   
Shiro did, but he had been desperate. He doesn’t say anything else and while he does not enjoy the idea that everyone is judging his decisions, he doesn’t regret making it if it assures Matt’s return.

Still, the other two humans look unconvinced. “You know that…” Lance starts, but before he can say anything else, Shiro stops him.

“I’ve researched this,” he assures him, serious, “I know what I’m doing, Lance.” 

He hopes he actually does.

  
  


Lance and Keith don’t get along. Pidge and Keith don’t interact much, but when they do is stilled and awkward. Hunk tries, but it’s obvious he doesn’t trust Keith and it shows in his posture.

Keith, however, is the biggest mystery of them all.

At this point he has been with them a month, but he hasn’t really opened much. He should have guessed that having a demon lurk around would be like that. The only reason Keith is even  _ with _ them and not appearing out of thin air when Shiro needs him, is because Shiro had chosen to keep the knife he had bounded Keith’s corporeal form next to him at all times.

Still, Keith doesn’t really interact with them. 

He mostly stands by the window and looks out; sometimes he watches Shiro work with a pensive look in his eyes. It feels like he’s studying him, searching for something. Shiro isn’t sure what, and until the other asks, there is nothing he can do to help him.

  
  


The first time they go out for a mission is two months in, when they finally think they have a lead worth following. It’s the first time Shiro actually sees Keith come alive, flame dancing around his frame.

He looks like a real demon now, with purple eyes and an aggressive stance. He destroys the other demons like they are nothing, and Shiro watches him in awe. 

There is no movement wasted, every single one of Keith’s strikes is made for a reason, and it almost looks like he’s dancing. In the dark night, his flames look like fireflies and Shiro is enthralled by them. 

Everyone had always told him to be careful, that evil had a certain way of luring you in. He doesn’t think any of them meant exactly this.

  
  


That night, he makes chocolate for both himself and Keith. From what he knows demon don’t usually eat or need human food, but there is nothing prohibiting them from eating them. 

So he goes to Keith’s spot under the window and offers it to him. Keith looks startled by that, and he looks at the offered beverage like he thinks it might kill him.

“What is this?” Keith asks, sniffing a little. His ears move with the motion, and Shiro has to refrain from laughing. He looks like a cat, really, and Shiro has always liked cats.

“This,” he says, shaking the mug, “is chocolate. Is very good, and we’re celebrating.”

Keith looks confused for a second, but he accepts the offering and Shiro smiles at him. He hesitates a second but, in the end, he sits down beside the demon.

It’s closer than they have ever been, and he can feel the way Keith is twitching beside him.

“You’re not scared of me,” Keith tells him. It’s not a question but a statement, so Shiro doesn’t really know what the other wants him to say. 

“Why would I be?” he asks, with a little smile, “you already have my soul. I don’t think it can get worse than that.”   
“Your soul is still inside you now,” Keith point out. But he seems to be disinterested in the conversation and he’s looking at the hot chocolate. He smells it again, and then licks the ridge where a single smudge of chocolate sits. 

The next second he takes a sip, and Shiro watches as the other’s tail moves languidly at his side. 

“It might be inside of me, but we both know it’s slowly rotting away,” Shiro comments, without any real heat. Shiro had known full well what happened to people who forged a contract with a demon. Their soul would stay in the body until the end of the mission, but it would start to corrupt slowly. If the quest took too long to be completed, Shiro’s body would start to rot away like his soul.

He could become a demon, and then, the contract would become void. It’s in the demon’s best interest to fulfill the human’s wish as soon as possible.

“You’re awfully friendly to me,” Keith says after a while. “I don’t understand.”

Shiro sighs and looks at his own drink. He imagines people might be angry at Keith, but it had been Shiro’s choice to resort to this. Can he fault a demon his own nature?

Still, he knows the others do. He sees it every day in the way they treat Keith. In how they look at him and, in turn, at Shiro.

“You’re helping me. I chose to do this,” Shiro explains in the end. “Also you’ve been… very kind ever since you’ve been here.”

Keith looks up, startled. “Kind?” he repeats, unbelieving, and Shiro smiles.

“I know the others have been hard on you, but you have always acted calm with them,” he stops and smiles, “not what I expected by a demon of anger.”

Keith seems surprised for a second at the idea that Shiro had been paying attention and he just goes back to his drink. Shiro is happy to just sip in silence, when he feels something close on his left calf.

He looks down to see Keith’s tail, wrapped around it, but when he looks up at the demon, the other isn’t looking at him

A part of him wants to ask for an explanation, but he doesn’t dare to.

They just finish their hot chocolate and then stay there a little time more.

  
  


Time passes and they keep trying to find a way to help Matt. Their days are spent researching and looking at old myths surrounding Zarkon. It seems like he’s a powerful demon, old enough that most of what they find on him is hearsay or just unbelievably difficult to find.

But sometimes, when Shiro’s eyes are too tired to read or they are all just too exhausted to do anything, he and Keith migrate to that little sofa under the window.

It becomes kind of a ritual, and every time Keith’s tail wraps itself around Shiro — something his wrist, sometimes his hand, sometimes his calf. It’s nice, and his fur is soft under Shiro’s skin, so much so that one day Shiro reaches forward and touches his ear.

Keith looks startled, until now the only one who had started any kind of physical contact between them.

Shiro fears for a second that he has pushed some kind of rule, that Keith will just jump back and broke this strange little connection that they have, but the demon relaxes under his fingers and allows Shiro to touch him.

He looks happy when Shiro moves his hand and he can’t do much else but smile. Keith seems to have relaxed to his presence, mellowing out under his hand. Shiro can’t do much more but appreciate it.

It’s just little moments of time, little glimpses in between the rest of their life.

Sometimes Shiro thinks they are the only things that keep him going, and while he can’t know what Keith thinks about it, he doesn’t care.

Maybe the demon is doing it only because of their pact, because of Shiro damnation, but it’s what Shiro needs. So he takes it.

 

However, for all they do and for how much they try, they don’t actually manage to find out much. Zarkon seems to be a whisper in the night, a nightmare when you go to sleep, but no one actually has any useful information about him.

In months he sees Pidge unrelenting spirit dimmer; Lance’s positivity losing its energy and even Hunk seems to be taking it hard. They are tired and depressed by the lack of actual results.

They have tried every old library, every master of the occult they know, every language that exists on earth.

Even Keith, who has no actual real stake in this if not for Shiro’s soul, looks fidgety and unhappy about the outcome. He’s probably thinking that he won’t be able to collect Shiro’s soul if they never manage to figure out anything about Zarkon.

Almost a year passes when one day Shiro looks himself in the mirror and sees it. 

He knows perfectly what are the consequences of bounding one soul to a demon, but it still shocks him the moment he notices that his hand is completely black. He had been feeling a little tingle in his fingers, but seeing it now makes him drop his cellphone.

He raises his left hand to his eyes and looks at it. His flesh looks rotten, corrupted to its very core. But isn’t that what Shiro is now?   
Not even all that human. 

He had decided long ago that any price would be worth Matt’s return, but he wonders now if he’s ready to lose himself for nothing at all.

Shiro startles the moment he feels something touch his still raised hand and he realizes he hadn’t hear Keith enter. The demon is touching his now completely black hand and looking in Shiro’s eyes.

In the year they have been together, their little moments of peace had become much more frequent. So much so that sometimes Shiro thinks it’s the only thing that allows him to breathe some days.

He knows that demons probably don’t have the ability to care about humans, but Shiro is now officially more demon than not. He wonders if that makes it better or worse.

“It’s started,” Keith says. He seems sad, but Shiro doesn’t have anything to say to him.

“We knew it would happen,” he settles for in the end, but Keith doesn’t look convinced.

He touches Shiro’s wrist and then the patch of skin where the now black skin touches the normal one. He seems focused, lost.

“We could have been faster,” Keith says, low. And Shiro wonders if that would have made anything better. If they had done it quicker, then Shiro would have just lost his soul much easier. His body would have been left a servant for Keith.

In the end, he guesses it would have been better for the demon.

“The important thing is that we do it,” Shiro says, determined, “I don’t care what happens to me after. What you decide to do. What I become.”

Keith looks at him and there is something strange in his eyes, so much so that Shiro feels compelled to add, “you knew this would happen. You made this contract.”

“Yeah,” Keith admits, a little winded, “we could have done it faster,” the demon repeats, looking at Shiro in the eyes, “and then I wouldn’t have cared.”   
It feels like an admission that Shiro doesn’t deserve, something that leaves him breathless. Keith doesn’t stick around after that, vanishing.

Shiro doesn’t move for a while.

  
  


In the end it takes another four months for them to finally find Zarkon. Shiro’s entire arm is now engulfed in the corrupted flesh, and while he can’t look at it, he discovers it has its use.

Shiro’s arm is stronger now, almost on par with a demon, and when he faces against Zarkon he uses it to deal the last and final blow.

He paints over the corpse of the higher demon and watches as Pidge runs to her brother. After a year prisoner of Zarkon, Matt looks more dead than alive, but Keith assures them he’s fine.  He will always be a little more demonic than human, much like Shiro, but  _ unlike _ Shiro, he will be free.

At the end of the battle Shiro looks up at Keith and feels his soul leave his body. He faints on the spot, feeling all the energy leave him.

The contract is complete.

  
  


He hears Keith touch his face and he wakes up slowly. He doesn’t feel all that different. Honestly he had imagined not having a soul to be something completely life changing, to be felt deep in his bones.

Shiro feels the same as always.

When he opens his eyes Keith is there, looking at him with a deep and focused expression.

“What happened?” he asks, but Keith shakes his head.

“We don’t have a lot of time,” Keith explains, “Lance has done… something. You have your soul back for a while. Do another pact with me.”

Shiro looks surprised, and confused. What does that mean.

“You already have my soul,” he says, trying to make sense of anything, “what more do you need?”

Keith growls, low and guttural; but it seems more desperate than angry. “I don’t want it,” he says, touching his face, “make another contract with me. I’ll make you the guardian of my souls.”

“What does that mean?” he asks, because he had never heard of anything like it. 

“It’s something demons can do,” Keith explains, frantic, “if they want one human to remain himself. It’s… rare. Most of my kind doesn’t care,” he admits, a little ashamed, “but it would allow you to remain… you.”

“Why?” Shiro can’t help but ask, feeling some of his energy leave him already. Whatever Lance did, it’s expiring already. 

“Because I  _ care _ ,” Keith admits, like it costs him something. He wonders if demons really can feel. He wonders how he would feel, being a container for all the souls that Keith has collected over the years.

However, does he really have any options?

“Okay,” he answers, looking in Keith’s eyes, “okay.”

Keith smiles and then he’s kissing him, biting into his lips enough to draw blood. A blood oath then, since Shiro’s soul can’t be used as a bargaining chip. Shiro closes his eyes and feels energy rush back into him.

He reaches for Keith’s back, pushing the demon closer to his body, unashamed. He’s too tired to refuse the urges, and for better or for worse, Keith had admitted he  _ cared _ about Shiro.

When the kiss ends, Shiro feels strange. It’s like he can feel himself, something filling him up with some kind of energy.

He realizes he can feel his own soul inside him, but nothing else.

“You don’t have any more souls?” Shiro asks, frowning. Because he can’t feel anyone else inside of him, at least he doesn’t think so.

“I don’t sign contracts with every human I see, Shiro, I’m not a novice,” Keith says, with a smirk, quoting what Shiro had said to Pidge that first day. 

“To be fair, you did sign one with me,” Shiro says, smiling and Keith just strokes his face.

“Yeah, I guess I did.”

And Shiro will never be completely right or completely human ever again, but Matt is safe, and he still has his soul.

He guesses his own stupidity could have landed him in a much worse situation.

**Author's Note:**

> As always comments and kudos help in time of need (and stress. Totally self-caused stress but still). And again I'm sorry about the mistakes that surely are in here D:  
> And if you want to chat a little or idk, you can find me on twitter @chiapslock and tumblr @fatty-arbuckle


End file.
